[Help-bash] Simplest way to keep trailing newlines when reading a file into a bash variable

[Peng Yu]

On the following thread, it discusses many ways to keep trailing
newlines in command substitution. But all the solutions require some
extra code that is not very convenient.

https://unix.stackexchange.com/questions/383217/

It is simple to read a file with training newlines removed into a bash variable.

x=$(< file)

Supposedly, it should be reasonable to expect a solution with as
little code as possible (e.g., no intermediate variable, one line).
But I haven't found such a solution. Does anybody know such a simplest
solution? Thanks.

-- 
Regards,
Peng